如何创建灰度直颜色选择器

Question

我需要实现一个灰度颜色选择器，我需要将它放在画布旁边的画布上，这样当用户点击灰度颜色选择器时，他会选择一个灰色阴影。

请看这个例子：

Answer 1

找到解决方案。

对于那些可能感兴趣的人：

public class ColorPickerView extends View {
private OnCustomEventListener mListener;
private Paint mPaint;
private Paint mPaint1;
private Paint mPaint2;

private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
public int color;

public ColorPickerView(Context context, AttributeSet attrs) {
    super( context,  attrs);

    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);
    mPaint = new Paint();
    mPaint.setAlpha(0x80);
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(0x44000000);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.BUTT);
    mPaint.setStrokeWidth(5);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);

}

@Override
protected void onDraw(Canvas canvas) {
    //canvas.drawColor(0xFFAAAAAA);

    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

    LinearGradient grad = new LinearGradient(0, 0, canvas.getWidth(), 0, Color.WHITE, Color.BLACK, TileMode.CLAMP);

    /* Draw your gradient to the top of your bitmap. */
    Paint p = new Paint();
    p.setStyle(Style.FILL);
    p.setShader(grad);
    canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), p);

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setDither(true);
    paint.setColor(0xFF00B8F5);
    paint.setLinearText(true);
    paint.setTextSize(60);

    canvas.drawText("SELECT COLOUR", mBitmap.getWidth()/4-40, mBitmap.getHeight()/3*2+5, paint);



}

private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

private void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;
    color= (int) (x/mBitmap.getWidth()*255);
    if(mListener!=null) mListener.onEvent();
}

private void touch_move(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();
    Path npath=new Path();
    npath.moveTo(mX, mY);
    npath.lineTo( x ,y );
    mX=x;
    mY=y;
    //mCanvas.drawPath(npath, mPaint);
    npath.reset();

}

private void touch_up() {

}

@Override
public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touch_start(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_MOVE:
        touch_move( event);
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        touch_up();
        invalidate();
        break;
    }
    return true;
}
public interface OnCustomEventListener{
    public void onEvent();
    }

    public void setCustomEventListener(OnCustomEventListener eventListener) {
    mListener=eventListener;
    }
}